In the days after early voting started in Georgia last month, sorority parties broke out around Atlanta.

In suburban Mableton, Ga., dozens of women wearing the pink and green colors of their sorority, Alpha Kappa Alpha, danced the “Cha-Cha Slide” on a grassy patch next to a strip mall. Two counties over, other members held a gathering, anchored by Beyoncé songs and free deli food, in a park. South of downtown, another get-together’s music was so loud that it turned the heads of people driving by.

Polls show a close presidential race, and these sorority-hosted events were aimed at persuading people to vote. Ms. Harris, a member of Alpha Kappa Alpha since her days at Howard University, has remained a loyal member of the first Black sorority, and plenty of her sisters are thrilled to see one of their own running for president.